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Linux Fundamentals

Introduction to Linux​

Linux is a powerful and flexible open-source operating system widely used in servers, desktops, embedded systems, and more. Understanding Linux fundamentals is crucial for anyone working in IT, cybersecurity, or software development.

Why Learn Linux?​

  • Open Source: Linux is free and open-source, allowing users to modify and distribute the software.
  • Security: Linux is known for its strong security model, making it a preferred choice for servers and critical systems.
  • Stability: Linux systems are highly stable and can run for long periods without needing a reboot.
  • Community Support: A large, active community provides extensive documentation, forums, and tools.

Basic Linux Commands​

  • ls: Lists files and directories in the current directory.
  • cd: Changes the current directory.
  • pwd: Prints the current working directory.

Example:

  • Navigates to the home directory using ~.
cd ~
  • This shows what directory you are currently on.
pwd
  • List all files in the current directory including hidden files.
ls -la

Managing Files and Directories​

  • touch: Creates a file
  • cp: Copies files or directories.
  • mv: Moves or renames files or directories.
  • rm: Removes files or directories.
  • mkdir: Creates a new directory.

Example:

  • Creates a file named file.txt.
touch file.txt
  • Creates a copy of file.txt named copiedFile.txt in the current directory using ..
cp file.txt copiedFile.txt
info

You can autocomplete the name of the existing file or a directory by pressing the Tab key.

  • Renames copiedFile.txt to renamedFile.txt.
mv copiedFile.txt renamedFile.txt
  • Deletes a file.
rm renamedFile.txt
  • Another way of deleting a file but it's not advisable.
mv file.txt /dev/null
  • Creates a directory named new_directory.
mkdir new_directory
  • Removes a directory named new_directory by specifying -r meaning recursive.
rm -r new_directory

Viewing and Editing Files​

  • cat: Displays the contents of a file.
  • less: Views the contents of a file page by page.
  • nano: Opens a file in the Nano text editor.
  • vim: Opens a file in the Vim text editor.

Example:

  • Shows the content of a file.
cat file.txt
  • Similar to cat but with scrolling when the content is large.
less file.txt
  • Edits a file using Nano.
nano file.txt
  • Edits a file using Vim.
vim file.txt
Exiting Vim

If you're stuck in Vim. You can exit without saving changes by pressing Esc 3 times (or more) and typing :q! and Enter.

User and Permission Management​

  • sudo: Executes a command as the superuser or another user.
  • chmod: Changes file or directory permissions.
  • chown: Changes the owner of a file or directory.
  • passwd: Changes the user password.

Example:

  • Similar to checking for updates in Windows.
sudo apt-get update
  • Updates all your packages.
sudo apt-get upgrade

Checking Network Configuration​

  • Installs network-related commands.
sudo apt install net-tools
  • Displays network interfaces and their configurations.
ifconfig
  • Displays network connections, routing tables, and interface statistics.
netstat

Tests connectivity to another host.

ping google.com
Cancelling commands

You can cancel commands by pressing Ctrl + C. In most linux terminals, you copy text using the Ctrl + Shift + C command.

External Resources​